Mechanical air conditioning and refrigeration are accomplished by continuously circulating, evaporating, and condensing a fixed supply of refrigerant in a closed system. Charging or recharging an air conditioning or refrigeration system with refrigerant is done through the low side suction intake fitting with the use of manifold gauges and service hoses. There are several types of refrigerants used and some can be charged as a vapor and others must be charged as a liquid.
For example, R-410A is replacing R-22 refrigerant and is a mixture of HFC-32 and HFC-125, and is thus considered to be zeotropic. Zeotropic refrigerants such as R-410A must be charged as a liquid from a canister due to the possibility of fractionation of the blend of refrigerants it contains. The range of temperatures at which components in the blended components of R-410A refrigerant boil (temperature glide) is <0.3° F., making it a near-azeotropic refrigerant mixture.
Since the different components of zeotropic refrigerants such as R-410A have different boiling points, the components fractionate during boiling. That is, as the temperature increases, the lower boiling point components vaporize first. The vapor thus has a higher concentration of the lower boiling components than the liquid, and a lower concentration of the higher boiling components. When such a fluid blend is stored in a closed container in which there is a vapor space above the liquid, the composition of the vapor is different from the composition of the liquid. If the fluid is then removed from the container to charge an air conditioning system, for example, fractionation can take place, with accompanying changes in composition. Such changes can cause a refrigerant to have a composition outside of specified limits, to have different performance properties or even to become hazardous, such as by becoming flammable.
In general, R-410A pressures are 1.8 times higher than those of R-22, and can be over 600 psi. CO2 is an example of another refrigerant gas that can run at a much higher pressure, as high as 1800 psi or more.
Low-pressure vapor refrigerant is compressed and discharged from the compressor as a high temperature, high-pressure, “superheated” vapor or liquid. The high-pressure refrigerant flows to the condenser, where it is changed to a low temperature, high-pressure liquid. It then flows through a filter dryer to a thermal expansion valve or TXV. The TXV meters the correct amount of liquid refrigerant into an evaporator. As the TXV meters the refrigerant, the high-pressure liquid changes to a low pressure, low temperature, saturated liquid/vapor. This saturated liquid/vapor enters the evaporator and is changed to a low pressure, dry vapor. The low pressure, dry vapor is then returned to the compressor. The cycle then repeats.
Because of the relatively high pressures involved, difficulties have arisen in removing fittings, such as anti-blowback fittings, coupled to high pressure, such as the hose connecting the high side of a refrigeration unit to the refrigerant source. The high pressure puts force on the connection, making it difficult to remove the fitting, especially manually.
It therefore would be desirable to provide a fitting that is easily removed from a high-pressure connection. It would be particularly desirable to provide a fitting that is easily removed from a high-pressure connection manually, i.e., without the need for a tool to apply torque to the fitting greater than can be applied by hand.